CN102944884B - GNSS receiver detects and eliminates the method for arrowband interference - Google Patents
GNSS receiver detects and eliminates the method for arrowband interference Download PDFInfo
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Abstract
This application discloses a kind of GNSS receiver to detect and the method eliminating arrowband interference, first, the time-domain signal received is converted to frequency-region signal by FFT conversion by receiver; Secondly, in this frequency-region signal, find the Frequency point of narrow-band interference signal, and these Frequency points are set to the blocking frequency of trapper; Finally, receiver by the time-domain signal that receives again by described trapper with filtering narrow-band interference signal.The application possesses skills and realizes the advantage comparatively simple, calculated amount is less, real-time, dirigibility is good.
Description
Technical field
The application relates to a kind of signal processing technology, particularly relates to a kind of detection to arrowband interference and removing method.
Background technology
The dipper system of the gps system of the U.S., Muscovite GLONASS (GLONASS) system, China, Galileo (Galileo) system etc. in Europe.Each GNSS system at least comprises GNSS satellite and GNSS receiver two parts, and GNSS receiver determines self position at the earth's surface by receiving GNSS satellite signal.
GNSS satellite signal adopts spread spectrum communication mode (Spread Spectrum Communication, spread spectrum communication) usually, is namely used for the signal bandwidth of transmission information much larger than the required minimum bandwidth of transmitted breath.
GNSS receiver, when receiving GNSS satellite signal, can be subject to various electromagnetic interference (EMI).Common interference source comprises wireless communication system, TV station, radio station, radar, harmonic wave that the internal clocking of ionospheric scintillation, even GNSS receiver produces also can bring interference to GNSS receiver.
According to the bandwidth of the undesired signal size relative to the bandwidth of GNSS satellite signal, arrowband can be roughly divided into disturb and broadband interference two kinds.A special case of arrowband interference is mono-tone interference, i.e. the continuous wave CO_2 laser of sine or cosine form, and its concentration of energy on a single frequency.The interference of remaining arrowband can regard as the superposition of the mono-tone interference of negligible amounts.The frequency of arrowband interference is more close to the centre frequency of GNSS satellite signal, and it is more serious on the impact of receiver.Arrowband interference can make GNSS receiver capture wrong relevant peaks, follow the tracks of in the frequency of mistake, and its positioning precision is reduced.
Refer to Fig. 1, a kind of existing GNSS receiver detects and eliminates the method disturbed arrowband and is:
First, the time-domain signal received is converted to frequency-region signal by FFT conversion (Fast Fourier Transform (FFT)) by receiver;
Secondly, in this frequency-region signal, find the Frequency point of narrow-band interference signal, and the power on these Frequency points is eliminated.
Refer to Fig. 2, because GNSS satellite signal adopts spread spectrum communication mode, thus its energy is distributed evenly on very wide frequency band, and power spectrum density is extremely low.The energy of narrow-band interference signal is then intensively distributed on very narrow frequency band and (can be considered the set of the Frequency point of negligible amounts), and power spectrum density is high.In frequency-region signal, receiver only needs to find out the Frequency point that power spectrum density significantly becomes large, the Frequency point of Here it is narrow-band interference signal.Then, the power of these Frequency points is set to 0 or be set to consistent with the power of the Frequency point of its periphery by receiver, can eliminate arrowband interference.
Finally, frequency-region signal is converted to time-domain signal by FFT inverse transformation (Fast Fourier Transform Inverse (FFTI)) again, carries out follow-up despreading process.
This method has following shortcoming:
One, owing to needing the time-domain signal received GNSS receiver in real time to carry out FFT conversion and FFT inverse transformation, complicated technology realization, and calculated amount is very large.
Its two, the spread-spectrum signal that GNSS receiver receives through said method process need consume the regular hour, thus real-time is poor.
GNSS receiver, for the Received signal strength eliminated after interference, also needs to carry out signal capture and signal trace successively.When carrying out signal capture process, due to lower to accuracy requirement, usually also adopting FFT to convert and the Received signal strength of time domain and local regeneration pseudo-code are converted to the calculating that is multiplied at frequency domain in the correlation computations of time domain, thus reducing capture time.And when the signal trace process carried out afterwards, due to higher to accuracy requirement, usually adopt the mode of directly time-domain signal being carried out to correlation computations.
Refer to Fig. 6, this be the existing GNSS receiver shown in Fig. 1 detect and eliminate arrowband interference method after followed by the process flow diagram carrying out signal capture and signal trace.It first carries out signal capture process to the frequency-region signal eliminated after arrowband interference, then carries out signal trace process to the time-domain signal eliminated after arrowband interference.
Refer to Fig. 3, another kind of existing GNSS receiver detects and eliminates the method disturbed arrowband and is: when the Frequency point that known arrowband disturbs, arrange one or more trapper (rejection filter), fallen by the target signal filter of these Frequency points.But this method needs the Frequency point knowing that arrowband disturbs in advance, this is a difficult problem; And the narrow-band interference signal entered suddenly cannot be tackled.There is again a kind of improvement for this reason, namely adopt adaptive notch filter (sef-adapting filter).This Frequency point not needing to know that arrowband disturbs in advance of improving one's methods, but the complexity that technology realizes is high, calculated amount large, and need certain stabilization time.
Summary of the invention
Technical problems to be solved in this application are to provide a kind of GNSS receiver and detect and the method eliminating arrowband interference, make technology realize comparatively simple, calculated amount is less.
For solving the problems of the technologies described above, the application's GNSS receiver detects and eliminates the method disturbed arrowband and comprises the steps:
1st step, the time-domain signal received is converted to frequency-region signal by FFT conversion by receiver;
2nd step, finds the Frequency point of narrow-band interference signal and at frequency domain filtering narrow-band interference signal, and these Frequency points is set to the blocking frequency of trapper in this frequency-region signal;
3rd step, receiver by the time-domain signal that receives again by described trapper with at time domain filtering narrow-band interference signal;
4th step, carries out signal capture process to the frequency-region signal eliminated after arrowband interference, then carries out signal trace process to the time-domain signal eliminated after arrowband interference.
The application's GNSS receiver detects and eliminates the method tool disturbed arrowband and has the following advantages:
One, have employed the method that spectrum analysis combines with trapper, and spectrum analysis can tackle the narrow-band interference signal entered suddenly, and this just improves the dirigibility detecting and eliminate narrow-band interference signal; And trapper drastically increases processing speed for the calculating of FFT inverse transformation, also just improve the real-time detecting and eliminate narrow-band interference signal.
Its two, only need to carry out FFT conversion, need not FFT inverse transformation be carried out, thus technology realize comparatively simple, calculated amount is less.Because GNSS receiver is in signal capture process, usually also adopts FFT to convert and Received signal strength and local regeneration pseudo-code are converted to the calculating that is multiplied at frequency domain in the correlation computations of time domain, thus reduce capture time.Thus the application is in order to spectrum analysis FFT arithmetic element used, can be multiplexing with the FFT arithmetic element in signal capture process, thus saves hardware resource.
Its three, adopt and there is the trapper of fixing blocking frequency, but not adaptive notch filter, thus reduce hard-wired complexity.Received signal strength after method process described in the application, ensure that acquisition sensitivity, tracking sensitivity and navigation accuracy not by the impact of narrow-band interference signal.
Accompanying drawing explanation
Fig. 1 is that a kind of existing GNSS receiver detects and eliminates the process flow diagram of the method for arrowband interference;
Fig. 2 is the schematic diagram of the frequency spectrum (frequency-region signal) of GNSS satellite signal and narrow-band interference signal;
Fig. 3 is that another kind of existing GNSS receiver detects and eliminates the process flow diagram of the method for arrowband interference;
Fig. 4 is that the GNSS receiver of the application detects and eliminates the process flow diagram of the method for arrowband interference;
Fig. 5 is the process flow diagram of a preferred embodiment of the application.
Fig. 6 is the whole process figure that a kind of existing GNSS receiver carries out signal transacting;
Fig. 7 a, Fig. 7 b are two kinds of whole process figure that the GNSS receiver of the application carries out signal transacting.
Embodiment
Refer to Fig. 4, the application's GNSS receiver detects and eliminates the method disturbed arrowband and is:
First, the time-domain signal received is converted to frequency-region signal by FFT conversion by receiver.
Secondly, according to the bandwidth of GNSS satellite signal and power spectrum density is low, the frequency band of narrow-band interference signal is narrow and the feature that power spectrum density is high, receiver is found out power spectrum density in frequency-region signal and is significantly become large Frequency point, the Frequency point of Here it is narrow-band interference signal.These frequency bands or Frequency point are set to the blocking frequency of one or more trapper by receiver.
Finally, receiver by the time-domain signal that receives again by described one or more trapper with filtering narrow-band interference signal.During filtering, can be 0 by the energy filtering of described Frequency point, can be also roughly the same with the energy of periphery Frequency point by the energy filtering of described Frequency point.
After above-mentioned process, GNSS receiver just by clean for the narrow-band interference signal filtering be mingled with in the time-domain signal received, can proceed the operations such as despreading thereafter.
Be described in detail with the technical scheme of a preferred embodiment to the application below, it specifically comprises the steps: as shown in Figure 5
1st step, receiver by receive analog radio-frequency signal mixing, filtering, obtain analog if signal;
2nd step, analog if signal by analog to digital conversion, is obtained digital medium-frequency signal by receiver;
3rd step, receiver, by digital medium-frequency signal mixing, filtering, obtains digital baseband signal;
4th step, receiver carries out FFT conversion to digital baseband signal, obtains its frequency spectrum;
5th step, in the frequency spectrum of digital baseband signal, the Frequency point that power spectrum density significantly becomes large found out by receiver;
6th step, the Frequency point that the 5th step is found out is set to the rejection frequency of trapper by receiver;
7th step, receiver by digital baseband signal through described trapper filtering, be eliminated arrowband interference after digital baseband signal.
In described method the 4th step, digital baseband signal is the plural xin (m) after the mixing of N point, m=0,1 ..., N-1.N point FFT conversion is adopted to obtain its frequency spectrum:
n=0,1 ..., N-1.
In described method the 5th step, can first calculate power magnitude Abs_dat (n) of each frequency=| F_data (n) |, n=0,1 ..., N-1.Then this N point power magnitude is averaged
using the M of this average P doubly as threshold value, M > 1.Then power magnitude is found to be greater than T Frequency point Fn (i) of this threshold value MP, i=0,1 ..., T-1.T is the natural number of >=2.Last alternatively to the Frequency point of this T narrow-band interference signal according to the descending sequence of power magnitude.
In described method the 6th step, if the quantity >=T of trapper, then by Frequency point Fn (i) of this T narrow-band interference signal, i=0,1 ..., T-1 is set to the blocking frequency of each trapper respectively.If the quantity of trapper is K, K is the natural number of < T, then by the Frequency point of T narrow-band interference signal according to the blocking frequency that K is set to each trapper respectively before after the descending sequence of power magnitude.
In described method the 7th step, if there is multiple trapper cascade to arrange.
Refer to Fig. 7 a, this is that the GNSS receiver of the application shown in Fig. 4 detects and followed by a kind of process flow diagram carrying out signal capture and signal trace after eliminating the method for arrowband interference.The power of the Frequency point of narrow-band interference signal is directly set to 0 at frequency domain by it, or is set to roughly the same with the power of periphery Frequency point.Then signal capture process is carried out to the frequency-region signal eliminated after arrowband interference, then signal trace process is carried out to the time-domain signal eliminated after arrowband interference.This implementation method only needs the calculating carrying out a FFT conversion to received signal.
Refer to Fig. 7 b, this is that the GNSS receiver of the application shown in Fig. 4 detects and followed by the another kind of process flow diagram carrying out signal capture and signal trace after eliminating the method for arrowband interference.The time-domain signal eliminated after arrowband interference is first converted to frequency-region signal by FFT conversion by it, then carries out signal capture process to the frequency-region signal eliminated after arrowband interference, then carries out signal trace process to the time-domain signal eliminated after arrowband interference.This implementation method needs to carry out twice FFT conversion to received signal, but can share a FFT computing unit to save hardware resource.
These are only the preferred embodiment of the application, and be not used in restriction the application.For a person skilled in the art, the application can have various modifications and variations.Within all spirit in the application and principle, any amendment done, equivalent replacement, improvement etc., within the protection domain that all should be included in the application.
Claims (8)
1. GNSS receiver detects and eliminates a method for arrowband interference, it is characterized in that, comprises the steps:
1st step, the time-domain signal received is converted to frequency-region signal by FFT conversion by receiver;
2nd step, finds the Frequency point of narrow-band interference signal and at frequency domain filtering narrow-band interference signal, and these Frequency points is set to the blocking frequency of trapper in this frequency-region signal;
3rd step, receiver by the time-domain signal that receives again by described trapper with at time domain filtering narrow-band interference signal;
4th step, carries out signal capture process to the frequency-region signal eliminated after arrowband interference, then carries out signal trace process to the time-domain signal eliminated after arrowband interference.
2. GNSS receiver according to claim 1 detects and eliminates the method for arrowband interference, it is characterized in that, according to the bandwidth of GNSS satellite signal and power spectrum density is low, the frequency band of narrow-band interference signal is narrow and the feature that power spectrum density is high, receiver is found out power spectrum density in frequency-region signal and is significantly become large Frequency point, the Frequency point of Here it is narrow-band interference signal.
3. GNSS receiver according to claim 1 detects and eliminates the method for arrowband interference, it is characterized in that, during filtering narrow-band interference signal, or be 0 by the energy filtering of described Frequency point, or be roughly the same with the energy of periphery Frequency point by the energy filtering of described Frequency point.
4. GNSS receiver according to claim 1 detects and eliminates the method for arrowband interference, it is characterized in that, comprises each step of following order:
Receiver by receive analog radio-frequency signal mixing, filtering, obtain analog if signal;
Analog if signal by analog to digital conversion, is obtained digital medium-frequency signal by receiver;
Receiver, by digital medium-frequency signal mixing, filtering, obtains digital baseband signal;
Receiver carries out FFT conversion to digital baseband signal, obtains its frequency spectrum;
In the frequency spectrum of digital baseband signal, the Frequency point that power spectrum density significantly becomes large found out by receiver;
Found out Frequency point is set to the rejection frequency of trapper by receiver;
Receiver by digital baseband signal through described trapper filtering, be eliminated arrowband interference after digital baseband signal.
5. GNSS receiver according to claim 4 detects and eliminates the method for arrowband interference, it is characterized in that, in the step of described " in the frequency spectrum of digital baseband signal; the Frequency point that power spectrum density significantly becomes large found out by receiver ", first the power magnitude of each frequency is calculated, then the power magnitude of this multiple frequency is averaged, using the certain multiple of this average as threshold value, then find power magnitude to be greater than the one or more Frequency point of this threshold value.
6. GNSS receiver according to claim 5 detects and eliminates the method for arrowband interference, it is characterized in that, in the step of described " in the frequency spectrum of digital baseband signal; the Frequency point that power spectrum density significantly becomes large found out by receiver ", finally also to the Frequency point of the one or more narrow-band interference signal according to the descending sequence of power magnitude.
7. GNSS receiver according to claim 4 detects and eliminates the method for arrowband interference, it is characterized in that, in the step of described " found out Frequency point is set to the rejection frequency of trapper by receiver ", when the quantity of the Frequency point of the quantity >=narrow-band interference signal of trapper, the Frequency point of each narrow-band interference signal is set to respectively the blocking frequency of each trapper;
When the quantity that the quantity of trapper is the Frequency point of K, K < narrow-band interference signal, by the Frequency point of this multiple narrow-band interference signal according to the blocking frequency that K is set to each trapper respectively before after the descending sequence of power magnitude.
8. GNSS receiver according to claim 4 detects and eliminates the method for arrowband interference, it is characterized in that, described " receiver by digital baseband signal through described trapper filtering; be eliminated arrowband interference after digital baseband signal " step in, if there is multiple trapper, cascade arrange.
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| CN111308285B (en) * | 2020-03-03 | 2021-04-13 | 西南交通大学 | Narrow-band interference noise reduction method |
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| CN114745024B (en) * | 2022-04-18 | 2024-03-26 | 中国电子科技集团公司第五十四研究所 | Spread spectrum signal demodulation device based on narrowband interference self-adaptive elimination |
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